The present invention relates to an apparatus and a method of measuring a flying behavior of a flying body, the apparatus and method being capable of measuring the flying behavior of the spherical flying body such as a golf ball with ease and high precision.
Measurement of the flying behavior of flying bodies is currently performed. For example, the flying behavior of a golf ball immediately after impact is measured by using images, based on which image measurements are made for simulating the carry distance of the golf ball.
A variety of flying behaviors of a golf ball may be found by using image measurement, such as velocity and movement direction. The velocity and angles of movement of a golf ball can be found by recording images at points in time with a predetermined interval of time therebetween, extracting the outline of each golf ball image, finding the center-of-mass point of each outline, measuring the distance between each center-of-mass point, and measuring the angle of movement of the center-of-mass point. In this case the extraction of the outlines of the golf ball can be performed at high precision, and therefore the velocity and the launch angle can be measured at high precision.
Further, a variety of measuring apparatuses and methods or measurement that measure the flying behavior of a golf ball, including rotational motion (spin) of the golf ball, have been proposed (refer to JP 2003-57258 A and JP 2000-19186 A, for example).
JP 2003-57258 A discloses a moving body motion parameter measuring apparatus capable of making accurate measurements of the velocity, motion direction, rotational angular velocity, and rotation direction of a moving body by using only one camera. In particular, the moving body motion parameter measuring apparatus can accurately measure initial trajectory parameters of a golf ball such as the initial velocity and launch angle of a golf ball immediately after being struck, and rotational angular velocity and rotation direction of the golf ball.
Referring to FIG. 13, specific marks are applied to the golf ball in order for the moving body motion parameter measuring apparatus to measure the spin of the golf ball.
A first golf ball image 102 and a second golf ball image 104 are recorded in one planar image 100 as shown in FIG. 13. Marks 106, 108, and 110 are provided to the first golf ball image 102 and to the second golf ball image 104.
It should be noted that the first golf ball image 102 and the second golf ball image 104 are represented as extracted outlines at points in time with a predetermined interval of time therebetween.
In JP 2003-57258 A, the positions of the marks 106, 108, and 110 in the first golf ball image 102 are tracked to the marks 106, 108, and 110, respectively, in the second golf ball image 104, and the rotation amount of the golf ball is computed.
The spin rate of the golf ball can thus be found in JP 2003-57258 A by tracking and locating the positions of the marks 106, 108, and 110 after a predetermined period of time has elapsed.
Further, JP 2000-19186 A discloses a method of measuring the rotational motion of a golf ball. The rotational motion of a hit golf ball is measured with this method from a projected image by photographing the hit golf ball using two cameras disposed along the flight line direction of the hit golf ball with a space therebetween. A golf ball on which a convex polygon shaped mark are printed onto a surface of the golf ball in black or a similar dark color to black is used with this method of measuring the rotational motion of a golf ball. The position of the convex polygon shaped mark through automatic image processing performed by a computer on photographed images, without any human labor involved, and the rotational motion of the hit golf ball is computed based on changes in the angular positions between the photographed images taken by the two cameras.
Referring to FIG. 14, an isosceles triangle shaped mark 125 is provided on the golf ball in the method disclosed by JP 2000-19186 A.
In this case two golf ball images 122 and 124 are recorded onto one frame 120 as shown in FIG. 14. The golf ball images 122 and 124 are recorded at points in time with a predetermined interval of time therebetween and undergo outline extraction.
The positions of the angle portions 126, 128, and 130 of the mark 125 in the golf ball image 122 are tracked to the angle portions 126, 128, and 130, respectively, of the mark 125 in the golf ball image 124, and the rotation amount of the golf ball is computed.
The backspin rate and side spin rate on the golf ball can thus be found by locating the positions of the marks after a predetermined period of time has elapsed.
The inventions disclosed in JP 2003-57258 A and JP 2000-19186 A both find the amount of rotation of a golf ball by providing a mark or marks on the golf ball for measurement of the amount of rotation of a golf ball, and by tracking the marks on images of the golf ball photographed at points in time with a predetermined interval of time therebetween.
Accordingly, the amount of rotation of the golf ball can be found by tracking the marks in the case where the golf ball rotates about a rotation axis that is perpendicular to the photographed surface of the golf ball.
However, a portion of the mark will be hidden, and the entire mark will thus be unable to be photographed, if the golf ball rotates about a rotation axis that is parallel to the photographed surface of the golf ball. The marks being tracked may be hidden in part, and thus there is a fear that the precision in measuring the rotation amount of the golf ball will decrease. In addition, it becomes necessary to change the measurement conditions or the like in order to prevent the mark from thus being hidden. Then, another problem will exist in that changes to settings on the measurement apparatus are unavoidable because measurement conditions are changed. Measurement work thus becomes complex.